Reinstalled El Capitan 10.11.1 with the supposed bettered USB problems. My main problem was that it kept running down my Bose Companion 5 Speakers and the mail application gobbled up all my memory, and I have a lot 32 gigs. My machine iMac 27 late 2013, 3.2 intel i5, 32 gig ram, 1024 nvidea video. Uo until now it seems to be running OK without the previous problems mentioned. Still not totally convinced. Will be posting the good and the bad.